| Description: | The em_sysenter function in arch/x86/kvm/emulate.c in the Linux kernel before 3.18.5, when the guest OS lacks SYSENTER MSR initialization, allows guest OS users to gain guest OS privileges or cause a denial of service (guest OS crash) by triggering use of a 16-bit code segment for emulation of a SYSENTER instruction. A flaw was discovered in the Kernel Virtual Machine's (KVM) emulation of the SYSTENTER instruction when the guest OS does not initialize the SYSENTER MSRs. A guest OS user could exploit this flaw to cause a denial of service of the guest OS (crash) or potentially gain privileges on the guest OS.
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